Semi-private forum for members contributing to the US Hawks Hang Gliding Training Manual

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I got the code working to import a model from the JavaScript version into Blender for rendering.

Here's the Falcon:

Falcon_3_195_2017_01_07.jpeg (27.77 KiB) Viewed 4180 times

Here's the SkySail:

SkySail_2017_01_07.jpeg (21.84 KiB) Viewed 4180 times

I took both shots from below to show the structure. Notice that the crossbar on the SkySail goes through the sail. That's hopefully not the way it was really built!!

The battens are working well for the root and tip, and that allows things like the reverse curve on the SkySail's tip (probably also not accurate). The SkySail drawing didn't show some of those details, but maybe Frank can help me get it right some time.

The main things to do are support double surface designs, varying tube diameters, and intermediate battens.

The curves are the top of an "Eppler 387" airfoil. I used it because I had the airfoil on a 35mm slide, so by using a projector and moving the distance to the screen, which was picnic table paper taped to my wall, I could draw the curve for the different lengths of ribs of a tapered wing. For the Skysail model (and my RC gliders) I used an old enlarger to project the airfoil onto paper where I could draw it.

This was an airfoil that I liked to use for my RC glider designs but, of course, using only the top curve in the Skysail made it a different airfoil.

Later, I wished I had used a more highly cambered curve, for a higher lift wing, but I would also have to add more twist for pitch stability..

How much easier it would be now with AutoCad and a computer.

BTW - I should get my Skysail model plan, the one I used to sell, scanned and I could post that. It's a large format so I can't scan it but maybe Kinkos could. It not only has the drawing but a lot of instructional text about building it. It has the rib 1:1 scale drawings. The model described in the $2.00 plan was a 2' span.

There's no need to bother with an actual scan for this project. You could just take a snapshot with your camera and post a reduced size image (maybe 2k x 2k). You could even sketch it on a napkin from memory and post a snapshot of the napkin.

The computer models I'm building are just for show ... not actual flying. We might use them for our training manual or a history section or just for decorations on the web site. Also, a first approximation is easily updated. We're not bending any real metal here.

There is a lot of fine print on the model plan, so I don't know if I can pick it up well enough with my camera but I'm going to try that first. I want it in digital storage since all I have now are the remaining paper prints of the plan. I also gave one of those to Ken DeRussey in 2012.

I did something like that about a dozen years ago. I had a lifetime of paper photos (thousands) that I wanted to digitize. I designed and used an L-shaped contraption to hold the photos and the camera. The long part of the "L" was a flat horizontal board to hold the camera which was mounted on a heavy chunk of rectangular steel. The camera holder could slide around, but it had enough weight to generally stay put. The short part of the "L" was a vertical board (about a foot square) for mounting each photo. It had a foot square of inch-thick porous foam mounted on the camera side. The vertical board had a hole in the center for a vacuum cleaner nozzle to provide suction through the foam. So I could simply place each photo onto the foam and the vacuum would hold it flat and in place. Click. Next photo. Click. Next photo. It was quite a bit faster than using a typical scanner.

I used small strips of paper for registration. They would also stay put on the foam. I adjusted them when I changed photo sizes so I could place each photo right where it needed to be very quickly.

I tried a few different artificial light sources, but they all produced a noticable gradient in the picture. I ended up just doing it outside on a sunny day.

With regard to the Skysail model, there's no immediate need. There are lots of other gliders to keep me busy. Maybe you can just describe it to me in person the next time we fly at Dockweiler.